The invention is directed to inorganic oxide materials having mesopores as well as micropores, or mesopores with a reduced amount of micropores or micropores with a reduced amount of mesopores and to a process for the preparation thereof.
Zeolites and related materials possess well-arranged pore systems and display uniform pore sizes. However, these materials tend to possess either only micro- or only mesopores. Furthermore these materials are rather expensive to produce.
There is a need for inorganic materials and in particular catalytic materials (or catalytic supports) that include both meso- and micro-pores.
There is also a need for new procedures for producing inorganic materials that contain mesopores and/or micropores.
Accordingly, in accordance with the invention, there is provided an inorganic oxide material having a pore structure, wherein at least part of its pores are in the mesopore size range and a part are in the micropore size range, and a method for producing such material as well as materials that contain essentially only mesopores (less than three volume percent and generally less than two volume percent of micropores) in an easy, inexpensive, and reproducible manner.
Furthermore, it is an object of the present invention to provide a silicate material that can easily be modified to have advantageous properties, such as specific catalytic properties for example, by replacing part of the silicon atoms by metal atoms such as aluminium, titanium, vanadium, gallium, iron and the like. Other objects and advantages will become clear from the subsequent description.
In accordance with an aspect of the invention, inorganic oxides that include micropores and mesopores can be prepared in an easy and simple manner by the use of certain compounds, resulting in materials having advantageous properties, such as specific pore structure, high pore volume and the ability to be modified, both on the surface and in the material itself.
In a preferred embodiment, the material of the invention is an amorphous inorganic oxide (preferably a silicate), having a bimodal structure of micropores and mesopores, domains of said micropores being connected to said mesopores, wherein the average mesopore size, determined by N2-porosimetry, is between 2 and 25 nm, and the average micropore size, determined by N2-porosimetry, is between 0.7 and 2.0 nm, preferably between 0.5 and 1.5 nm.
In accordance with one aspect of the present invention, the mesopores of the material have a defined pore size distribution. More particularly, the pore size distribution of the mesopores is such that in a pore size distribution plot wherein the derivative of pore volume is plotted on the y-axis and the pore diameter is plotted on the x-axis, in such a plot, the ratio of the width of the plot at the point of the y-axis .which is one-half of the height of the plot, to the pore diameter at the maximum height of the plot is no greater than 0.75 and is preferably no less than 0.01. More preferably such ratio is no greater than 0.5.